[PATCH] cfq-iosched: Kill O(N) runtime of cfq_resort_rr_list() (53b03744) · Commits · 戴 / test

block/cfq-iosched.c

+22 −31

Original line number	Diff line number	Diff line
		@@ -152,7 +152,6 @@ struct cfq_queue {
		unsigned long slice_start;
		unsigned long slice_end;
		unsigned long slice_left;
		unsigned long service_last;

		/* number of requests that are on the dispatch list */
		int on_dispatch[2];
		@@ -174,6 +173,7 @@ enum cfqq_state_flags {
		CFQ_CFQQ_FLAG_fifo_expire,
		CFQ_CFQQ_FLAG_idle_window,
		CFQ_CFQQ_FLAG_prio_changed,
		CFQ_CFQQ_FLAG_queue_new,
		};

		#define CFQ_CFQQ_FNS(name) \
		@@ -198,6 +198,7 @@ CFQ_CFQQ_FNS(must_dispatch);
		CFQ_CFQQ_FNS(fifo_expire);
		CFQ_CFQQ_FNS(idle_window);
		CFQ_CFQQ_FNS(prio_changed);
		CFQ_CFQQ_FNS(queue_new);
		#undef CFQ_CFQQ_FNS

		static struct cfq_queue cfq_find_cfq_hash(struct cfq_data , unsigned int, unsigned short);
		@@ -350,7 +351,7 @@ cfq_find_next_rq(struct cfq_data cfqd, struct cfq_queue cfqq,
		static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
		{
		struct cfq_data *cfqd = cfqq->cfqd;
		struct list_head list, entry;
		struct list_head *list;

		BUG_ON(!cfq_cfqq_on_rr(cfqq));

		@@ -375,31 +376,26 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
		}

		/*
		* if queue was preempted, just add to front to be fair. busy_rr
		* isn't sorted, but insert at the back for fairness.
		* If this queue was preempted or is new (never been serviced), let
		* it be added first for fairness but beind other new queues.
		* Otherwise, just add to the back of the list.
		*/
		if (preempted \|\| list == &cfqd->busy_rr) {
		if (preempted)
		list = list->prev;
		if (preempted \|\| cfq_cfqq_queue_new(cfqq)) {
		struct list_head *n = list;
		struct cfq_queue *__cfqq;

		list_add_tail(&cfqq->cfq_list, list);
		return;
		}
		while (n->next != list) {
		__cfqq = list_entry_cfqq(n->next);
		if (!cfq_cfqq_queue_new(__cfqq))
		break;

		/*
		* sort by when queue was last serviced
		*/
		entry = list;
		while ((entry = entry->prev) != list) {
		struct cfq_queue *__cfqq = list_entry_cfqq(entry);
		n = n->next;
		}

		if (!__cfqq->service_last)
		break;
		if (time_before(__cfqq->service_last, cfqq->service_last))
		break;
		list = n;
		}

		list_add(&cfqq->cfq_list, entry);
		list_add_tail(&cfqq->cfq_list, list);
		}

		/*
		@@ -591,13 +587,12 @@ __cfq_slice_expired(struct cfq_data cfqd, struct cfq_queue cfqq,
		if (cfq_cfqq_wait_request(cfqq))
		del_timer(&cfqd->idle_slice_timer);

		if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
		cfqq->service_last = now;
		if (!preempted && !cfq_cfqq_dispatched(cfqq))
		cfq_schedule_dispatch(cfqd);
		}

		cfq_clear_cfqq_must_dispatch(cfqq);
		cfq_clear_cfqq_wait_request(cfqq);
		cfq_clear_cfqq_queue_new(cfqq);

		/*
		* store what was left of this slice, if the queue idled out
		@@ -1297,13 +1292,13 @@ retry:
		hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
		atomic_set(&cfqq->ref, 0);
		cfqq->cfqd = cfqd;
		cfqq->service_last = 0;
		/*
		* set ->slice_left to allow preemption for a new process
		*/
		cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
		cfq_mark_cfqq_idle_window(cfqq);
		cfq_mark_cfqq_prio_changed(cfqq);
		cfq_mark_cfqq_queue_new(cfqq);
		cfq_init_prio_data(cfqq);
		}

		@@ -1672,12 +1667,8 @@ static void cfq_completed_request(request_queue_t q, struct request rq)
		if (!cfq_class_idle(cfqq))
		cfqd->last_end_request = now;

		if (!cfq_cfqq_dispatched(cfqq)) {
		if (cfq_cfqq_on_rr(cfqq)) {
		cfqq->service_last = now;
		if (!cfq_cfqq_dispatched(cfqq) && cfq_cfqq_on_rr(cfqq))
		cfq_resort_rr_list(cfqq, 0);
		}
		}

		if (sync)
		RQ_CIC(rq)->last_end_request = now;

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